If you’ve decided you want to stretch your own canvas, you’ll need to select your materials. The bars you stretch the canvas on are just as important as the canvas for determining the final product. You may wish narrow bars so that the painting is easier to frame or deep bars so that it looks good unframed. If you are planning a very large canvas then you will want to consider the tension that all that tight canvas will exert on the bars – your canvas could be pulled out of shape – so stronger bars (thicker or with aluminium) would be appropriate. Here are some things to consider when choosing your stretcher bars.
What are Stretcher Bars?
All stretcher bars differ from plain timber in that they are shaped to have a flat back and a slanted front that has a higher edge along the outside of each bar length. This may be accomplished with bars that slope downward toward the centre of the frame or by adding a raised lip around the edge. You staple on the flat, back side and the canvas is stretched so that it floats over the slanted front and only touches the outer rim. This is to prevent a ridge of paint forming when the canvas comes in contact with the bar when the brush pushes the canvas towards the bar as you paint.
Characteristics of Each Type
The Professional and Museum ranges are the bars that most artists use. The Alu-Pro range of bars is for those artists who wish to invest in the highest quality bars.
For very large sizes you will need to choose thicker bars for strength, so the thinner bars aren’t available in the largest sizes.
The ‘depth’ refers to the profile, the measurement of how far the canvas will protrude from the wall when hung as a painting.
These bars can be purchased in pairs for stretching your own canvas and they are also used in our ready-made canvases and bespoke canvases.
The Jackson’s Professional Range
wooden in 3 depths – 18mm, 21mm, 43mm
- Strong – but for larger canvases where the canvas tension will be greater, the thicker 43mm bars will be stronger than the narrower.
- The 18mm depth is available in inch sizes, in 2-inch increments up to 40 inches. These 2 inch size bars (and the 21mm bars as well) are for artists who might need to match an inch-sized frame or an existing inch-sized painting where cm-sized canvases would be in partial fractions of inches, or for those who prefer Imperial measurements.
- The 21mm depth is available in inch sizes, in 2-inch increments up to 54 inches. These two narrow bars are not available in as long lengths as the deeper bars because they are not strong enough to be be that long without warping.
- The 43mm depth is available in 10cm increments up to 200cm long.
- Strong interlocking corners and a space for a wooden corner wedge.
- Made of wood – PEFC Certified kiln-dried fir.
Jackson’s Professional stretcher bars are available in 3 sizes.
The Jackson’s Museum Range
wooden in 2 depths – 20mm, 35mm
- Stronger because of the layers of laminated wood.
- Both depths are available in 5cm increments up to 200cm long.
- Strong interlocking corners and a space for a wooden corner wedge.
- Made of layers of wood – PEFC Certified kiln-dried pine.
Jackson’s Museum stretcher bars are available in 2 sizes.
The Jackson’s Alu-Pro Range
wood and aluminium in 2 depths – 25mm, 45mm
- The strongest because of the aluminium.
- Both depths are available in 10cm increments up to 200cm long.
- Corners need connector pieces to join them, which can be tightened in the same way that wooden wedges are used.
- Made of strong, light aluminium with a strip of wood on for stapling.
- Wood responds to temperature and humidity changes, it swells when it gets warm or moist and shrinks when it cold or dry. Aluminium does not change its dimensions. This stability means the canvas stretched across the bars is not subject to changes in tension and the paint layer should not be pushed and pulled so it will be less likely to crack over time. The patented design creates a perfect framework for canvas stretching, free from deformation, twist and warp. These are so sturdy that cross bars are optional, at any size.
Jackson’s Alu-Pro stretcher bars are available in 2 sizes.
Custom Sizes
When the stretcher bars are cut to a custom size the connector has to be changed from the original dovetail to this connector system, shown.
If you need a size that is not available as standard, Jackson’s can cut all three types of stretcher bar to bespoke lengths. The order will need to be placed on the phone. The price is the price of the bar that is one size larger on our price list as yours will be cut down from that – plus £10 per stretcher frame for the four new corner dovetail joiners, as these custom-cut bars use a different joining system.
Centre bar and cross bar – for added rigid strength to help prevent warping (and useful as a carry handle)
If a stretcher bar frame is very large it is a good idea to give it additional support by adding a bar across the back (a centre bar) or two bars across the back that cross one another (a cross bar). You can add a centre bar for strength (and to have a handle on the back) at any size that there is a slot in the bar to accomodate it.
You will need to use a centre bar that fits the stretcher bar – there is a different size for each size of bar – so there are 7 sizes/types of centre bars.
If the stretcher bar can only accommodate a centre bar and not a cross bar, or if you only need the added strength of a single centre bar, choose the bar to go across the width, not the length. So a 50x100cm canvas with a single centre bar would have a 50cm bar across the width. This provides more stability than if the centre bar were to go lengthwise.
For the 18mm and 21mm Professional stretcher bars the use of a centre bar is recommended when any side of the canvas exceeds 30 inches. The canvas can only accommodate a centre bar, they are not made to use a cross bar. Sizes starting at 28 inches have centre bar slots.
The 21mm and 18mm Professional bars can only take a single centre bar, a second cross bar is not possible.
Because the 18mm and 21mm bars are shallower they only have 1 slot for a centre bar and since they are not notched to overlap there can only be one cross bar.
For the 43mm Professional stretcher bars the use of a centre bar is recommended when any side of the canvas exceeds 100cm. Sizes starting at 80cm have centre bar slots. The 43mm bars are able to accommodate two crossing bars that pass one over the other for added strength (on two planes).
43mm Professional bars allow two cross bars to pass one over the other.
The 43mm Professional bars have two slots for centre bars.
In the 43mm Professional bars the two cross bars can pass one above another..
The Museum 20mm bars will accommodate a centre bar or a cross bar pair. Sizes starting at 50cm have centre bar slots. Centre bars 100cm and larger will have notch cut in the centre that allows two to be used in one layer (on the same plane) as the notched fit together.
The Museum 35mm bars will accomodate a centre bar or a cross bar pair. Sizes starting at 60cm have centre bar slots. Centre bars 100cm and larger will have notch cut in the centre that allows two to be used in one layer (on the same plane) as the notches fit together.
Because the Museum bars only have one slot they can have cross bars only if you use the notched centre bars.
The notched cross bars in place in the Museum bars.
Museo Alu-Pro bars will accomodate a centre bar or a cross bar pair. These are called primary cross bars (a single piece plus the necessary primary hardware connectors) and secondary crossbars (in two pieces plus the necessary secondary hardware connectors). They are only needed for very large sizes unless you wish to use then as handholds.
Jackson’s Alu-Pro with a single centre bar.
Jackson’s Alu-Pro cross bar.
The Length of the Centre Bar
Centre bars are smaller than the stretcher bars because they fit inside the rectangle, whereas the stretcher bars are sized based on the outside of the rectangle they produce. But we have already figured out the sizes that fit and they are labelled as the size needed for the rectangle, rather than the actual length of the bar. So a 50cm centre bar is not actually 50cm long itself, rather it is made to fit inside a 50cm stretcher bar.
Corner Tightening Wedges
Another name for the little triangular wooden pieces that come with your stretcher bars are keys.
New canvases often need to be tightened and old paintings can become loose over time and will need to be made more taut with corner tightening wedges.
If you are stretching a canvas – there is a space in the wooden centre bars for smaller wedges to be tapped in if the centre bar needs tightening, so there is a front and back orientation to the centre bar to ensure the slot is facing the back.
Read more about wedges in this earlier post: How to Use the Canvas Wedges That Come with a Canvas or Stretcher Bars.
How to assemble the stretcher bar frame
Read about assembling our ranges of wooden stretcher bars in this earlier post: How To Assemble Stretcher Bars for Canvas.
Read about assembling our ranges of Alu-pro stretcher bars in this earlier post: How To Assemble Stretcher Bars for Canvas.
43mm Professional bars assembled into two 160x180cm stretcher frames and two 160x200cm stretcher frames.
Stretching Canvas at Jackson’s Art
These stretcher bars and everything you need for stretching artist canvas are available at jacksonsart.com. Stretcher bars can be selected on the easy-to-use website and you can choose how you’d like them to be delivered to your studio.
- DIY Canvas Stretching – Stretcher Bars
- DIY Canvas Stretching – Canvas by the metre
- The Canvas Department
Postage on orders shipped standard to mainland UK addresses is free for orders of £39.
Do you know where I can buy 20x20cm
canvases which do not have the ridge on
the front of the wooden stretchers? I use
texture so cannot use these. I need the
front to be flat.
Hi Lynne
The ridge on the bars stops the imprint of the bar appearing on your canvas. As you paint on the surface you apply pressure, and without the ridge you’d get a line showing through on the paint work an inch(or so) in from the edge of the canvas. Therefore all good stretcher bars and canvases have this ridge. The canvas when it is stretched across is tight like a drum and is completely flat on the front, so you will be able to use these.
Many thanks
Lisa
Hi
I have a canvas about
100cm×120cm.How do i stretch the
canvas?
Thanks
Hi Alex, I think this blogpost on stretching canvas will help you, but do let us know if there’s anything else we can give you guidance on.
Hi,
I restretched an unfinished painting that I
had unstretched for transport and not sure
why or how to make the paintings edges
come into alignment with the stretcher bars.
overtime i do it somehow its a little off.
please advise. thank you.
Hi Leonardo
Yes, it is hard to get the painting back in alignment with the bars.
It helps if the canvas is being restretched on the same bars it was painted on originally. If it was then you can lay it face down and see where to put the stretcher and where the canvas should be folding up around. The main tip is to do the corners first.
Tension is difficult because the painting has to be tight but there is not much give in the primed surface so when you attempt to stretch it tight there is a risk of tearing the unprimed canvas you are pulling on.
You can start with one corner and staple that in place properly as you would when you finishing stretching the first time, with three staples in the corner folds and one or two either side. Then do the same on the diagonally opposite corner. This might not be too difficult because the stretcher itself will be giving a bit – the hard part comes next when you have to then stretch the other corners, because then the whole thing will be very tight, as tight as it was originally. This is the point where you have to really tug and it feels like it might rip.
Once all the corners are stapled in the right place then you can turn it over to check the alignment of the painting edges with the canvas edge and if it’s okay then you can turn it face down again and finish stapling the edges.
I hope that helps.
Hello,
I purchased a painting overseas from a local
artist and I am looking for some advice on
the correct method/stretcher bars before
hanging. The difficulty for me is that the
painting is 40″ x 70″ edge to edge and is not
standard canvas but on a cloth that has
some stretch along its weft resulting in a
little stretch along the bias. I intend to make
a frame with local wood from its country of
origin but I do not feel comfortable making a
stretcher for it. Any advice would be greatly
appreciated.
Thank you for your time.
Hi Darren
A lot of tension is used to stretch canvas and the wood can be pulled out of shape if it isn’t strong enough. So for anything over 30″ I recommend deep stretcher bars. The problem with this might be that you do not have any unpainted fabric on the edge to pull around the side and staple to the back. If that is the case you have two options. You can sew 4″ of fabric all around and then that can be stretched around the bars and stapled. The other option is to stretch a blank canvas the same size as your painting and then laminate your painting on top with acrylic gel or PVA. A number of famous contemporary artists do this, like Frank Bowling and Rose Wylie. The uneven edges of the painted fabric show and are a part of the overall look.
Since your fabric isn’t canvas I would be a bit concerned that it isn’t strong enough to withstand the tension of pulling tight as a drum and it might tear either during stretching or at the staples or sewn seam. Canvas is very strong and it still tears sometimes. It also might be a problem that your fabric has stretch, so there would probably be wrinkles and wavy ripples in the painting. You get those even with a plain weave canvas, it is hard to get even tension.
After thinking about all of this, I think what I would do is put it on a panel and frame that. You can stretch it around a panel just a bit smaller than the painting and string long cords across the back that you can cinch to pull it smooth, like upholstery. Or you can attach it to a panel with some sort of adhesive, if you use reversible PVA it can be removed later with water.
It sounds like a bit of a challenge but an interesting project. If you have time I’d love to see what you come up with.
Hi. If I am buying stetcher bars 1.8m and
1.4m am I ordering a 1.8m centre bar and
a 1.4m cross, or am I ordering a smaller
centre and cross bar to account for it
being inside the frames edge.
If so what size would I need
Thanks
jack
Hi Jack
Yes, centre bars are smaller than the stretcher bars because they fit inside the rectangle.
But we have already figured out the sizes that fit and they are labelled for that rather than their actual size. So a 50cm centre bar is not actually 50cm long itself, rather it is made to fit inside a 50cm stretcher bar. So you just need to buy the same size as the stretcher bar.
Thanks for pointing out that it isn’t clear. We will add some more info to clear it up.
How can you assemble large stretcher bars,
so the corners will be perfect 45 degree
angles?
Hi Gabriel
I use a diagonal measurement, when both diagonal measurements are the same, it is square (when the corner is ‘square’ it means it is at 90 degrees).
You can also use a method of putting something hard with a 90-degree corner inside the bars to check, like a CD case.
Both of these methods are shown in How To Assemble Stretcher Bars for Canvas. This link is in the post above, near the bottom.
Do you make up stretched canvases with Frames to specific sizes?
We make custom sizes of stretched canvases – you can order using our Bespoke Canvas Builder.
You start by selecting the type of stretcher bar you would like. The standard bars come in 2cm increments. Chose the Cut to Length bars if you’d like a size between, then we can do 1cm increments.
How do I know what size crossbars to buy? If
I’m buying stretcher’s at 79 x 85 in., how big
should my crossbars be? thanks!
Hello
You should buy the cross bars of the size of your stretcher. So a 100x200cm stretcher requires a 100cm and a 200cm cross bars. We have already compensated for the size difference in the interior dimensions.
Do you have a video showing how to notch
cross bars?
Hi Sue
The cross bars either come with notches that allow them to overlap or they do not, depending on the style. You do not do it yourself.
Some are designed to not need them and instead overlap by crossing on 2 different levels. Some bars do not have them because the length is so short that they assume you won’t need a cross bar for a little canvas.
Please advise if staples applied to fix the
canvas near the corners of stretcher bars
subsequently hinder the ability of the bars to
stretch, as they will likely have pinned the
mortise to the tendon.
Hi Michael
This later article covers that topic more
How to Stretch Canvas a Visual Guide
“Notice the line in the wood that is the join of the two bars. You will want the option of spreading that a bit with wedges if needed so always be aware of where those are and do not staple across them.”
It is ok to staple near them, just not across the line between the two, because the staple will fasten them together.
Hi, I’m looking for custom sized stretcher
with dovetail joint.
I saw the new joint system for custom-cut
bars but I’m wondering if you can make the
joint system like original dovetail for
custom-cut bars? It’d be really appreciated if
you can help this. Thank you!
Hi. The bars come in 5cm increments with the factory dovetails. If you need a length that is in between, so we must cut it in our warehouse, our machinery doesn’t allow us to do the original style joints.
Is it possible to adjust the size of your project?
Hello Julie, Very interesting article. I have
2 canvas – 1st one around 93cm (w) x 40
cm (h)
2nd – 83cm (w) x 121cm (h)
I would like to stretch them – Could you
please confirm how thick would I need the
stretcher bars to be as there are different
thickness? I am thinking the bigger one
would have to have a thicker bar in order
to support it.
Yes, you are right. As you get up to that size a thicker bar is needed so that the fabric doesn’t pull the wood out of square.
And cross bars are also recommended. So avoid the bars under 30mm.